Landing installation for landing a tethered balloon

ABSTRACT

An installation for landing a tethered balloon comprises a balloon which is brought back down towards the ground (9) by means (11) of a return cable (2), and which has a gondola (6) which is hollow in its center to allow the return cable (2) to pass therethrough, and it also includes means for winding the return cable (2) out and in, which means are mounted in a cavity (10) in the ground. According to the invention, the installation also includes a landing platform (3) covering the cavity (10) and including an opening (12) through which the return cable (2) passes, which opening is centered on the vertical outlet axis (12a) of the return cable (2). The landing platform (3) comprises the curved surface (3a, 3b) of at least one right truncated cone (13, 14) which is extended at its bottom by a substantially horizontal annular landing zone (15, 15&#39;) and which is centered on the vertical outlet axis (12a) of the return cable (2); the gondola (6) of the balloon (1) is fitted with at least three swivel-mounted wheels which are fixed beneath the gondola (6) in an annular zone of the same size as the landing zone (15, 15&#39;).

The present invention relates to a landing installation for landing atethered balloon which is brought back to the ground by means of areturn cable. It relates more particularly to an installation forenabling the gondola of a tethered balloon to be landed on a landingplatform in a position where it is centered relative to the verticaloutlet axis of the return cable.

In the present text, the term "balloon" designates a gas balloonconstituted by a gastight envelope which contains a gas that is lessdense than air and which, more particularly, is suitable for being heldcaptive in a net; the net is also secured to a load frame, from whichthe gondola is suspended. The gondola enables passengers to embark onboard the balloon.

A tethered balloon is a balloon connected to the ground. In a firstknown type of tethered balloon, the balloon is designed so as to becapable of being in equilibrium with the atmosphere at all times and itis connected to the ground by means of return cords. The function of thereturn cords is solely to oppose the drift effects of the wind byretaining the balloon in a space situated above a clear landing zone onthe ground lying between attachment points for the return cords. Undersuch circumstances, the balloon rises in the air and returns to theground with its own means; the gondola of the balloon lands within thelanding zone wherever it is taken by the wind.

In a second known type of tethered balloon, the balloon is designed sothat it always tends to rise in the air. Under such circumstances, it isbrought down to the ground by means of a return cable that passesthrough the center of the gondola and that has one end connected to theload frame. The other end of the return cable is wound onto a winchsystem which is mounted in a depression in the ground. The sole purposeof the depression is to house the winch system. With this second type oftethered balloon, the gondola never lands on the ground, but remainssuspended a few meters above the winch depression; passengers embark inthe gondola by means of a gangway.

It will readily be understood that with a tethered balloon of the secondtype, it is difficult, and indeed dangerous, for the passengers toembark on board the gondola because of the great instability of thegondola, particularly in the presence of wind. In order to mitigate thatdrawback, a first object of the present invention is to propose aninstallation enabling the gondola of a tethered balloon of the secondtype to be landed on a landing platform on the ground.

When a tethered balloon of the second type is moving up or down, theballoon is observed to be deflected slightly because of the wind, so thereturn cable is no longer vertical. Consequently, assuming that it isdesired to land the gondola of a tethered balloon of the second type ona landing platform that covers the depression containing the winchsystem, when the tethered balloon is brought back to the ground, thegondola reaches the platform off-center relative to the vertical outletaxis of the return cable. If the platform is plane, then the tetheredballoon lands and remains in its off-center position. It should beobserved that throughout the descent of the balloon, the gondola remainsin a substantially horizontal position. If no special precautions aretaken to recenter the gondola, it can happen that movements of theballoon, under the effect of wind and in particular when the winddirection reverses, put the suspension lines connecting the gondola tothe load frame back under tension, thereby entraining the gondola. Suchunwanted movements of the gondola when placed on the landing platformare prejudicial to proper embarkation or disembarkation of passengerswho run the risk of being injured.

A second object of the present invention is therefore to propose alanding installation for a tethered balloon of the second type thatenables the gondola of the tethered balloon to be landed in a positionthat is centered relative to the vertical outlet axis of the returncable.

These various objects are fully achieved by the landing installation ofthe invention for landing a tethered balloon, which installation, inconventional manner, comprises both a balloon which is brought down tothe ground by means of a return cable, with the gondola of the balloonhaving a hollow center through which the return cable passes, and meansfor winding the return cable out and in, which means are mounted in acavity in the ground.

In a manner characteristic of the invention, the landing installationfurther comprises a landing platform covering the cavity and includingan opening through which the return cable passes and which is centeredon the vertical outlet axis of the return cable; the landing platformconsists in the curved surface of at least one right truncated conewhich is extended at its bottom by a substantially horizontal annularlanding zone and which is centered on the vertical outlet axis of thereturn cable; the gondola of the tethered balloon is fitted with atleast three swivel-mounted wheels which are fixed beneath the gondola inan annular zone having the same dimensions as the landing zone.

In the installation of the invention, gondola landing can be subdividedinto three successive stages. During the first two stages the suspensionlines connecting the gondola to the load frame are always tensioned, andthe gondola is continuously suspended from the load frame which ispulled down towards the ground by the return cable. In the first stage,the gondola arrives over the landing platform in a position that issubstantially horizontal, but off-center relative to the vertical outletaxis of the return cable; none of the wheels of the gondola is yet incontact with the platform. In the second stage, at least one of theswivel-mounted wheels of the gondola comes into contact with the curvedsurface of a truncated cone; the gondola continues to move downwardsunder the combined effects of traction from the return cable and ofgravity, being guided by the swivel-mounted wheel on the surface of thetruncated cone towards the landing zone situated further down, until allof the swivel-mounted wheels of the gondola come into contact with thelanding zone. At the end of this second stage, the gondola is in aposition that is centered relative to the vertical outlet axis of thecable. In a third stage, the return cable continues to be wound in so asto relax all of the suspension lines connecting the gondola to the loadframe. The balloon can then move under the effect of the wind withoutputting the suspension lines under tension. The gondola is held securelystationary on the landing zone.

In a first particular embodiment, the curved surface of the landingplatform corresponds to the inside surface of a downwardly-directedhollow right truncated cone.

In a second particular embodiment, the curved surface of the landingplatform corresponds to the outside surface of an upwardly-directedright truncated cone; in which case the recess in the gondola forpassing the return cable must also be large enough to enable the gondolato receive said truncated cone during the second stage of landing.

In a preferred embodiment, combining the two particular embodimentsgiven above, the two truncated cones are concentric; the outside curvedsurface of the upwardly-directed truncated cone, referred to as the"inner" truncated cone, and the inside curved surface of thedownwardly-directed truncated cone, referred to as the "outer" truncatedcone, are interconnected by a single annular landing zone.

Advantageously, in this preferred embodiment, when the inner and outertruncated cones have the same angle at the apex, the gondola is fittedwith at least two pairs of swivel-mounted wheels which are fixed beneaththe gondola around a circle, the diameter of the circle being equal tothe inter-cone distance, with the two wheels in each pair beingdiametrically opposite. The term "inter-cone" distance is used herein tomean the maximum distance in a horizontal plane between the curvedsurfaces of the two truncated cones. Thus, during the second stage oflanding, when two diametrically opposite wheels are in contact with thelanding platform and in alignment with the vertical outlet axis of thereturn cable, one of them comes into contact with the curved surface ofone of the two truncated cones, e.g. the outer truncated cone, while theother comes into contact with the curved surface of the other truncatedcone, e.g. the inner truncated cone. The gondola is thus held accuratelyhorizontal, by the surfaces of the two truncated cones and by said twowheels which are situated in the same horizontal plane, and it continuesmoving down towards the landing zone while remaining in said position.Recentering of the tethered balloon during the second stage of landingis performed with very great stability for the gondola.

More particularly, in order for recentering of the tethered balloon tobe accurate, and for the wheels of the gondola to be locked in positionby the inside and outside curved surfaces of the outer and innertruncated cones when the gondola is placed on the landing zone, saidsurfaces intersect at a circle which corresponds to the landing zone. Inwhich case, the inter-cone distance corresponds to the diameter of thecircle.

In order to obtain optimum distribution of the weight of the gondolaover all of the swivel-mounted wheels, the base of the gondola is aregular polygon having n vertices, and it is fitted with nswivel-mounted wheels which are fixed on the diagonals of the polygon.The swivel-mounted wheels are preferably fixed on the inscribed circleof the polygon, which polygon is an octagon.

Other characteristics and advantages of the invention appear from thefollowing description of a preferred embodiment of an installation ofthe invention for landing a tethered balloon, which installation isgiven by way of non-limiting example and is described with reference tothe accompanying drawings, in which:

FIG. 1 is a diagram of an installation for landing a tethered balloonand including a plane landing platform;

FIG. 2 is a simplified plan view of the landing platform and theoctagonal gondola of the tethered balloon in a landing installation ofthe invention;

FIG. 3 is a side view of the FIG. 2 gondola;

FIG. 4 is a section view of the landing platform and of the gondola inthe landing installation of the invention when the gondola is in itsfinal approach stage to the landing platform;

FIG. 5 is a second view of the landing platform and of the gondola ofthe landing installation of the invention when the gondola is placed onthe landing zone, below the outlet opening of the return cable; and

FIG. 6 is a diagram showing another possible profile for the landingplatform of an installation of the invention.

With reference to FIG. 1, a presently known type of tethered ballooncomprises a balloon 1 which can be brought back down to the ground 9 bymeans of a return cable 2. The balloon 1 comprises a gastight envelope 4which is held captive in a net 5, and also a gondola 6 which issuspended from a load frame 7 secured to the net 5. In practice, thegastight envelope 4 contains helium and a ballonet of air under pressureso that the balloon 1 is always subjected to an upwardly directed force,also referred to as "lift", and always tends to move up through the airby its own means. The gondola 6 is connected to the load frame 7 bymeans of short suspension lines 8a and crossed lines 8b referred to as"bracing" lines. The gondola 6 is a body of revolution about a centralaxis of symmetry 6a and has a hollow center so as to pass the returncable 2 regardless of the angle of inclination that may be taken up bysaid cable. A cavity 10 is also formed in the ground 9 to serve as ahousing for a winch system 11 comprising a main drum 11a that is rotatedplus a deflection pulley 11b. A first end 2a of the return cable 2passes through the bottom 6b of the gondola 6 and is fixed symmetricallyaround the entire periphery of the load frame 7. The other end 2b iswound onto the main drum 11a after passing over the deflection pulley11b. The term "vertical outlet axis" of the return cable 2 is used inthe present text to designate the vertical axis 12a that is tangentialto the periphery of the deflection pulley 11b and that consequentlycorresponds to the vertical position which the return cable 2 is capableof taking up.

At present, during the operations of disembarking and of embarkingpassengers on board the gondola 6, a tethered balloon as described aboveis not designed to be brought right down onto the ground, but it remainssuspended in the air, a few meters above the cavity 10. One way ofenabling the balloon 1 to land on the ground 9 would be to cover thecavity 10 with a plane platform 3 as shown in FIG. 1. Under suchcircumstances, the platform 3 must necessarily include an opening 12allowing the return cable 2 to pass therethrough and which is centeredon the vertical outlet axis 12a. However, that solution suffersdrawbacks as described below.

When the gondola 6 rests on the platform 3 and the return cable 2 iswound out, the balloon 1 rises into the air by its own means. To bringit back down to the ground, the cable 2 is wound in onto the main drum11a of the winch. While the tethered balloon is moving up and down, thegondola 6 remains suspended from the load frame 7 via at least the shortsuspension lines 8a which remain constantly under tension. In theabsence of any wind, the cable 2 is vertical and coincides with its ownvertical outlet axis 12a. The load frame 7 remains horizontal and thebracing lines 8b remain relaxed so long as the angle between the bottom6b of the gondola and the horizontal remains smaller than an angle ofabout 8°. When this angle runs the risk of exceeding 8°, e.g. due to thegondola 6 being unbalanced by a bad distribution of passengers, then thebracing lines 8b come under tension and prevent said inclination of thebottom 6b of the gondola 6 exceeding 80 relative to the horizontal. Inthe presence of wind, the gastight envelope 4 of the tethered balloon 1is subjected to considerable lateral thrust forces which serve firstlyto incline the return cable 2 at an angle a relative to its verticaloutlet axis 12a, and secondly to tilt the assembly comprising thegastight envelope 4 and the load frame 7 through an angle β relative tothe vertical axis of symmetry 6a of the gondola 6. The gondola remainshorizontal so long as the angle of inclination β is less than or equalto 8°, which corresponds to an angle of inclination α of about 30°. Whenthe inclination of the load frame 7 exceeds 8°, the bracing lines 8bcome under tension and the gondola is entrained by the load frame 7. Asa result, the bracing lines 8b cause the bottom 6b of the gondola 6 toremain continuously substantially horizontal, thereby ensuring thecomfort of passengers on board the gondola 6.

In the presence of wind, when the tethered balloon 1 is brought backdown to the ground by winding in the return cable 2, the gondola 6 landson the platform 3 in a position that is off-center relative to thevertical outlet axis 12a of the return cable 2, as shown in FIG. 1. Theoffset between the axis of symmetry of the gondola 6 and the verticaloutlet axis 12a of the return cable 2 is a function of the angle α. Thesize of the platform 3 must therefore be designed as a function of thesize of the gondola 6, and the maximum values for the angle α and thesuspension lines 8a.

In the absence of wind, when the gondola 6 is placed on the landingplatform 3, and the return cable 2a has been sufficiently wound in ontothe main drum 11a, the suspension lines 8a and 8b are relaxed. In thepresence of wind, the gastight envelope 4 and the load frame 7 aredeflected relative to the vertical. If the gondola 6 is centeredrelative to the vertical outlet axis 12a of the return cable 2, then thedeflection cannot give rise to the suspension lines 8a being put undertension so the gondola 6 remains entirely stationary on the platform 3.In contrast, if the gondola 6 is in an off-center position relative tothe vertical outlet axis 12a, it can happen that the suspension lines 8awhich are up-wind are brought back under tension by the deflection ofthe load frame 7, thereby lifting the gondola 6 relative to the platform3.

The landing installation of the invention, a preferred embodiment ofwhich is described below, provides an improvement to the installation ofFIG. 1 in that the gondola 6 of the tethered balloon is fitted withswivel-mounted wheels and the landing platform 3 has a special profileenabling the gondola 6 to be recentered relative to the vertical outletaxis 12a of the return cable 2 during landing. This prevents any risk ofuntimely movement of the gondola under the effect of wind, once thegondola has been placed on the landing platform.

With reference to FIGS. 2 and 4, the platform 3 of the invention is notplane but is constituted by the outside curved surface 3a of an innertruncated cone 13 and by the inside curved surface 3b of an outertruncated cone 14 which is hollow. These truncated cones 13 and 14 aretruncated right cones centered on the vertical outlet axis 12a of thereturn cable 2. They are concentric and they have the same angle at theapex, however they are opposite ways round, the inner truncated cone 13being upwardly directly while the outer truncated cone 14 is downwardlydirected. The curved surfaces 3a and 3b intersect and where theyintersect they define a circular landing zone 15 of diameter D below theoutlet opening 12 of the return cable 2.

With reference to FIGS. 2 and 3, the bottom 6b of the gondola 6 of thetethered balloon 1 in a landing installation of the invention consistsin a bottom plate 16 having a hollow center and whose outside and insideperimeters 17a and 17b form two concentric octagons. On the top face 16aof the bottom plate 16, there is secured an outside metal frame 18 ofoctagonal shape, and on which eight vertical plates 18a are fixed sothat each plate 18a extends one of the sides of the octagonal outsideperimeter 17a vertically from the bottom plate 16. Similarly, anoctagonal inside metal frame 19 receives eight vertical plates 19a andis mounted on the inside perimeter 17b of the bottom plate 16. Thevertical uprights 19b of the inside metal frame 19 are taller than thevertical uprights 18b of the outside metal frame 18; their top ends 20are designed to be fixed to one of the ends of the suspension lines 8a,there being one suspension line 8a per vertical upright 19b, with theopposite end of each suspension line 8a being fixed to the periphery ofthe load frame 7.

The gondola 6 is also fitted with eight wheels 21a, 21b, 21c, 21d, 21e,21f, 21g, and 21h. Each wheel is mounted to rotate freely about ahorizontal axis 22 relative to a support 23 in the form of anupside-down U-shape. Each support 23 is swivel-mounted on the bottomface 16b of the bottom plate 16 about a vertical swivel axis 24. As aresult, the horizontal axis of rotation 22 of each wheel can take up anydirection. The supports 23 for the wheels 21a to 21h are also fixed tothe bottom face 16b of the octagonally-shaped bottom plate 16 in such amanner that the vertical swivel axes 24 thereof lie simultaneously onthe diagonals of the plate 16 and on a circle which is centered on thecentral axis of symmetry 6a of the bottom plate 16, with the diameter ofthe circle being equal to the diameter D of the landing zone 15. In theparticular embodiment shown in FIG. 2, the bottom plate 16 is sodimensioned relative to the two truncated cones 13 and 14 that saidcircle corresponds to the circle inscribed within the outside perimeter17a of the bottom plate 16, thereby making it possible to obtain verygood stability for the gondola on the ground.

In FIG. 4, the tethered balloon 1 is in its final stage of approachingthe platform 3 in the presence of wind. The gondola 6 is thereforeoff-center relative to the vertical outlet axis 12a of the return cable2. None of the wheels of the gondola 6 is yet in contact with one of thecurved surfaces 3a or 3b of the truncated cones 13 and 14. The gondola 6is suspended from the load frame 7, with all of its suspension lines 8abeing under tension. The bottom plate 16 of the gondola 6 lies in asubstantially horizontal plane.

When traction continues to be applied to the return cable 2, at least afirst wheel of the gondola 6 comes into contact with one of the twocurved surfaces 3a and 3b of the two truncated cones 13 and 14. Sincethe bottom plate 16 of the gondola is still substantially horizontal,this contact takes place either close to the ground 9 for the curvedsurface 3b of the outer truncated cone 14, or else close to the outletopening 12 of the return cable 2 on the curved surface 3a of the innertruncated cone 13.

In FIG. 2, dashed lines show two positions referenced A and B that maybe taken up, by way of example, by the outside perimeter 17b of thebottom plate 16 of the gondola 6 at the moment it comes into contactwith the landing platform 3. When the gondola 6 arrives off-centerrelative to the outlet vertical axis 12 of the return cable 2, and inthe particular position given reference A, only the wheel 21a comes intocontact with the curved surface 3b of the outer truncated cone 14, inthe immediate proximity of the ground 9. Because of the lift of theballoon 1, the wheel 21a can swivel about its vertical swivel axis 24,and it can take up a position defined by the slope of the curved surface3b. The gondola 6 which remains suspended from the load frame 7continues to move downwards under the effect of gravity and above all oftraction in the return cable 2 on the load frame 7 until it reaches thelower circular landing zone 15, being directed over the surface of theouter truncated cone 14 by the swivel-mounted wheel 21a. During thisdownward movement of the gondola 6, the inner truncated cone 3penetrates into the bottom plate 16. It is then up to the person skilledin the art to dimension the recess in the bottom plate 16 of the gondola6 as a function of the size of the inner truncated cone 6, and moreparticularly of its angle at the apex, and as a function of the heightof the swivel-mounted wheels of the gondola, so that the inner truncatedcone 13 can be received in the bottom of the gondola 6 without comingdirectly into contact with the bottom plate 16 of the gondola 6. Inpractice, the constraint that applies to the size of the hollow in thegondola 6 for passing the return cable 2 when it takes up its maximuminclination of 30° relative to the vertical is always large enough forthe inner truncated cone 13 to be capable of penetrating into thegondola 6. It should also be observed that it is not possible for one ofthe wheels of the gondola 6 to be caught in the outlet opening 12 of thereturn cable 2 that is formed through the apex of the inner truncatedcone 13. Consequently, the inner truncated cone 13 serves to protect thewinch system 11, and more particularly the deflection pulley 11b.

In the position referenced B, the two diametrically opposite wheels 21aand 21e are in alignment with the vertical outlet axis 12a of the returncable 2. Since the bottom plate 16 of the gondola 6 is substantiallyhorizontal, and since the distance between the two diametricallyopposite wheels 21a and 21e is equal to the diameter D of the circularzone 15, both of these two wheels 21a and 21e come into contact with theplatform 3. The wheel 21a is in contact with the curved surface 3b ofthe outer truncated cone 14 in the immediate proximity of the ground 9.The wheel 21e is in contact with the curved surface 3a of the innertruncated cone 13 in the immediate proximity of the outlet opening 12 ofthe return cable 2. In this case, both of the wheels 21a and 21e swivelso as to line up with the slope of the curved surface of thecorresponding truncated cone and the gondola 6 continues to movedownwards until it reaches the circular landing zone 15, being radiallyguided by the two wheels 21a and 21e on the surfaces of the inner andouter truncated cones 13 and 14.

Naturally the two characteristic landing positions described above withreference to FIG. 2 are not the only positions that can be taken up bythe gondola 6 at the moment of landing. For example, it is possible forthe gondola 6 to come into contact with the curved surface of one of thetwo truncated cones of the landing platform via two adjacent wheels, orvia a plurality of pairs of diametrically opposite wheels.

When the gondola 6 reaches the circular landing zone 15, all of itsswivel-mounted wheels 21a to 21h come into contact with the landing zone15. The gondola is then accurately recentered relative to the verticaloutlet axis 12a of the return cable 2. This is the position shown inFIG. 5. Thereafter the return cable 2 continues to be wound in until allof the suspension lines 8a are completely relaxed. Thus, when thegondola is in this centered position, with all of the suspension lines8a being kept slack by traction on the return cable 2, even if the loadframe 7 were to be inclined at a maximum angle β relative to thevertical, the suspension lines 8a cannot be put back under tension. As aresult the gondola 6 remains perfectly stationary in the circularlanding zone 15.

In a particular embodiment, the angles at the apex between the axes ofsymmetry of the truncated cones 13 and 14 and their respective surfaces3a and 3b was equal to 77°. The diameter D of the circular landing zonewas 5.36 meters. The distance between two diametrically oppositevertices of the outside perimeter 17a of the bottom plate 16 was 5.8meters. The distance between two diametrically opposite vertices of theoctagonal inside perimeter 17b of the bottom plate 16 of the gondola 6was 3.96 meters.

The invention is not limited to the preferred embodiment describedabove. It would be possible to design a landing platform with an innertruncated cone 13 only, the outer truncated cone 17 being replaced, forexample, by a horizontal annular landing zone. Conversely, it would alsobe possible to design a platform 3 with an outer truncated cone 14 only,the inner truncated cone 13 being replaced by a horizontal annularlanding zone. It is also possible within the ambit of the invention todesign a landing platform in which the curved surfaces of the inner andouter truncated cones 13 and 14 do not intersect but are interconnectedby a horizontal annular landing zone 15', as shown in the profile ofFIG. 6. In this case, the distance between two diametrically oppositewheels of the gondola 6, e.g. between the wheels referenced 21a and 21eshould be selected to lie between the minimum diameter d_(min) and themaximum diameter d_(max) of the annular landing zone 15'. This distanceis preferably selected to be equal to the inter-cone distance d whichcorresponds to the maximum distance in a horizontal plane between thecurved surfaces of the inner and outer truncated cones 13 and 14. Itshould be observed that this inter-cone distance d corresponds to thediameter D of the circular landing zone 15 when the curved surfaces 3aand 3b of the two truncated cones 13 and 14 intersect.

Each bottom plate 16 of the gondola 6 may be any regular polygon. Thebottom plate 16 may also be in the form of a ring.

We claim:
 1. A tethered balloon and landing installation therefor, thetethered balloon being brought back towards the ground by means of areturn cable, and including a gondola which has a hollow center throughwhich the return cable passes, and the installation including means forwinding out and in the return cable, which means are mounted in a cavityin the ground, the balloon and installation being characterized in thatthe installation further comprises a landing platform covering thecavity and including an opening through which the return cable passesand which is centered on a vertical outlet axis for the return cable, inthat firstly the landing platform is constituted by the curved surfaceof at least one right truncated cone which is extended at its bottom bya substantially horizontal annular landing zone and which is centered onthe vertical outlet axis for the return cable, and in that, secondly,the gondola of the balloon is fitted with at least three swivel-mountedwheels which are fixed beneath the gondola in an annular zone having thesame dimensions as the landing zone.
 2. A tethered balloon and landinginstallation thereof according to claim 1, characterized in that thecurved surface for the landing platform corresponds to the insidesurface of a downwardly directed hollow right truncated cone.
 3. Atethered balloon and landing installation thereof according to claim 1,characterized in that the curved surface of the landing platformcorresponds to the outside surface of an upwardly directed righttruncated cone, and in that the recess in the gondola for passing thereturn cable is large enough to enable the gondola to have saidtruncated cone pass therethrough.
 4. A tethered balloon and landinginstallation therefor according to claim 1, wherein the curved surfaceof the landing platform comprises two truncated cones, and an annularlanding zone interconnecting said two truncated cones, an wherein aninner cone of said cones is upwardly directed, whereas an outer of saidcones is downwardly directed.
 5. A tethered balloon and landinginstallation therefor according to claim 4, characterized in that theoutside and inside curved surfaces of the two inner and outer truncatedcones intersect at a circle which corresponds to the landing zone.
 6. Atethered balloon and landing installation therefor according to claim 5,characterized in that the base of the gondola is a regular polygonhaving n vertices, and is fitted with n swivel-mounted wheels which arefixed on the diagonals of the polygon.
 7. A tethered balloon and landinginstallation therefor according to claim 6, characterized in that theswivel-mounted wheels are fixed on the inscribed circle of the polygon.8. A tethered balloon and landing installation therefor according toclaim 4, characterized in that the base of the gondola is an octagon. 9.A tethered balloon and landing installation therefor according to claim4 wherein the inner and outer truncated cones have the same angle at theapex, the gondola is fitted with at least two pairs of swivel-mountedwheels which are fixed beneath the gondola around a circle, the diameterof the circle being equal to the inter-cone distance with the two wheelsin a pair being diametrically opposite.
 10. A tethered balloon andlanding installation therefor according to claim 9, characterized inthat the base of the gondola is a regular polygon having n vertices, andis fitted with n swivel-mounted wheels which are fixed on the diagonalsof the polygon.
 11. A tethered balloon and landing installation thereforaccording to claim 9, characterized in that the outside and insidecurved surfaces of the two inner and outer truncated cones intersect ata circle which corresponds to the landing zone.
 12. A tethered balloonand landing installation therefor according to claim 11, characterizedin that the base of the gondola is a regular polygon having n vertices,and is fitted with n swivel-mounted wheels which are fixed on thediagonals of the polygon.
 13. A tethered balloon and landinginstallation therefor according to claim 12, characterized in that theswivel-mounted wheels are fixed on the inscribed circle of the polygon.14. A tethered balloon and landing installation therefor according toclaim 9, characterized in that the base of the gondola is an octagon.